The invention relates to performance modeling of a communications system, such as one that provides for communications of streaming data.
Traditional telephony communications are routed through circuit-switched networks between telephony end stations. An example of a circuit-switched network includes the public switched telephone network (PSTN). Telephony end stations may be connected through telephone lines to a central office system, or alternatively, the telephony end stations may be connected to a telephone exchange system that in turn is connected to the central office system or to other telephone exchange systems. Examples of telephone exchange systems include key telephone systems and private branch exchange (PBX) systems. In a circuit-switched network, end stations are provided dedicated end-to-end circuit connections for the duration of each call over which voice data may be communicated.
With improvements in the bandwidth and speed associated with packet-based networks, voice and other forms of streaming data communications over packet-based networks have become possible. Packet-based networks may be connection-oriented, such as Asynchronous Transfer Mode (ATM) or Frame Relay networks, in which virtual connections or circuits are provided between end stations to communicate the streaming data. Another type of packet-based network is the packet-switched, connectionless network, such as an Internet Protocol (IP) network.
In a packet-switched network, packets sent from a source may traverse different paths to arrive at the final destination. Such packets share the network bandwidth with conventional non-streaming data (such as data associated with electronic mail, file transfer, web access, and other traffic). The packets that are routed over separate paths are reassembled at the destination. Transmission speeds of the various paths may vary depending upon the usage of the network paths over which the packets are being transported. Also, during heavy traffic conditions, packets may be delayed and lost. During heavy usage of packet-switched networks, packet delays and losses may cause poor performance of voice communications. Voice data packets that are lost or delayed due to inadequate or unavailable capacity of packet-switched networks may result in gaps, silence, and clipping of audio at the receiving end.
Thus, a need exists for a method and apparatus that can determine the quality level of a communications system including packet-based networks.